Add RandomBytesIterator type

[nvzqz]

This turns all RandomBytesGenerator into infinite Sequences of their Bytes type.

This type allows for consuming and iterating over a RandomBytesGenerator without having to call randomBytes() directly. This mainly serves as a convenience.

This is different than Randoms- types because it doesn't take a mutable pointer to the source RandomGenerator. So, unless the iterator is shared, there is unique access to the generator.